Such torsional vibration dampers can be used for example in large two-stroke and four-stroke diesel engines and gas engines for counteracting torsional vibrations in the power train. The torsional vibration damper, which may have diameters of up to four meters, is, for example, flanged to a crankshaft of the engine. Torsional vibration dampers of the type mentioned above can also be used on other rotating parts such as camshafts, intermediate shafts and axle drive shafts, as well as gearboxes.
A torsional vibration damper of this type is known e.g. from EP 2 206 933 A1 corresponding to DE 10 2009 004 252 B1. In this damper the hydraulic damping effect is dominated by radial gaps that are formed between the outer housing and the inner part and that connect neighboring chambers.
In large torsional vibration dampers of this type additional bypasses are formed by one annular channel at an internal side wall of the outer housing. The length of the bypasses in circumferential direction is limited by the thickness of the leaf spring assemblies. FIG. 4 shows a conventional torsional vibration damper 1 having a ring 2 arranged in the annual channel 3 for adjusting the axial width of the bypasses 4 and thus the damping properties. This single ring 2 is concentric to the common axis of rotation of the outer housing 5 and inner part 6 and is adjustable via a plurality of screws 7. Such adjustment is required for example for compensating machining tolerances that can hardly be avoided for large diameters as well as for other reasons. The hydraulic damping effect created by these additional bypasses 4 is usually larger than that of the afore-mentioned overflow channels.
Adjustment of such a damper, in particular when being connected to a crankshaft inside a motor casing, requires opening a lid at the motor casing for access to the adjustment screws 7 and rotating the crank shaft screw by screw. In order to prevent excessive warping or twisting of the ring several turns of the crankshaft are required for achieving the desired amount of adjustment at each screw and corresponding axial gap since each screw has to be operated several times and usually cannot be rotated in its final position in one step to avoid too strong deformation of the ring 2.
Another torsional vibration damper is known from FR 1 375 156 wherein the damping force is controlled in response to centrifugal forces by spring-biased piston mechanisms. These spring-biased piston mechanisms are held in position by a screw plug, which, however, does not provide any option for adjustment. This mechanism is therefore not suitable for the above-described tuning of the damper after assembly. Further, FR 1 375 156 teaches a piston for controlling flow of damper medium between neighboring chambers rather than between sub-chambers of one and the same chamber.